Ciclosporin (or cyclosporin) is a cyclic oligopeptide with immunosuppressive and calcineurin inhibitory activity. It is characterised by a selective and reversible mechanism of immunosuppression. It selectively blocks the activation of T-lymphocytes by the production of certain cytokines which are involved in the regulation of these T-cells. This involves, in particular, the inhibition of the synthesis of interleukin-2 which, at the same time, suppresses the proliferation of cytotoxic T-lymphocytes which are responsible, for example, for the rejection of extraneous tissues. Ciclosporin acts intracellularly by binding to the so-called cyclophilines or immunophilines which belong to the family of proteins which bind ciclosporin with high affinity. The complex of ciclosporin and cyclophilin subsequently blocks the serine-threonine-phosphatase-calcineurin. Its activity state in turn controls the activation of transcription factors such as NF-KappaB or NFATp/c which play a decisive role in the activation of various cytokine genes including interleukin-2. This results in the arrest of the immunocompetent lymphocytes during the G0 or G1 phase of the cellular cycle since the proteins which are essential for cell division such as interleukin-2 can no longer be produced. T-helper cells which increase the activity of cytotoxic T-cells which are responsible for rejection are the preferred site of attack for ciclosporin.
Furthermore, ciclosporin inhibits the synthesis and release of further lymphokines which are responsible for the proliferation of mature cytotoxic T-lymphocytes and for other functions of the lymphocytes. The ability of ciclosporin to block interleukin-2 is critical for its clinical efficacy: transplant recipients which tolerate their transplants well are characterised by a low production of interleukin-2. Patients with manifest rejection reactions, on the contrary, show no inhibition of interleukin-2 production.
The first and so far only ciclosporin which has been placed on the market (in the 1980s) is ciclosporin A. Ciclosporin-A is defined chemically as cyclo-[[(E)-(2S,3R,4R)-3-hydroxy-4-methyl-2-(methylamino)-6-octenoyl]-L-2-aminobutyryl-N-methylglycyl-N-methyl-L-leucyl-L-valyl-N-methyl-L-leucyl-L-alanyl-D-alanyl-N-methyl-L-leucyl-N- methyl-L-leucyl-N-methyl-L-valyl]. Its availability initiated a new era in transplant medicine because, with its help, the proportion of transplanted organs which remain functional in the long term, could be increased substantially.
The first ciclosporin medicament (Sandimmun of Sandoz) could already increase the success rate in kidney transplantations by a factor of about 2. A new oral preparation of ciclosporin (Neoral of Sandoz, later Novartis) with higher and more reliable bioavailability allowed better dosing and further increase of the success rate since the 1990s. Despite some new developments of active agents, ciclosporin is still a frequently used agent in transplantation medicine.
Today, lung transplantations can, in principle also be carried out successfully if patients are treated with ciclosporin A. Since the introduction of this active agent in clinical therapy, the number of lung transplantations carried out worldwide has increased dramatically. This is true for both, the transplantation of a single lung as well as the transplantation of both lungs. Lung transplantations are normally contemplated in the case of patients with a final-staged lung disease where medicinal therapy has failed and life expectancy is short due to the disease. Transplantations of a single lung are indicated, for example, in the case of certain forms of emphysema and fibrosis, such as idiopathic pulmonary fibrosis. Both lungs are transplanted in cases of mucoviscidosis, primary pulmonary hypertension, emphysema with global insufficiency, frequent serious infections as well as idiopathic pulmonary fibrosis with complication by repeated infections.
In the case of a successful lung transplantation, the patients' quality of life can be increased again to an almost normal level. However, contrary to heart, kidney and liver transplantations, the survival times after lung transplantations are still relatively short and amount to an average of only 5 years. This might be due, amongst other things, to the fact that the active agent ciclosporin cannot be effectively dosed with all patients due to systemic side effects such as renal dysfunction, increased serum levels of creatinine and urea, renal damage with structural changes, for example, interstitial fibrosis, increased serum levels of bilirubine and liver enzymes, hypertrichiosis, tremor, fatigue, headache, gingivitis hypertrophicans, gastrointestinal complains like anorexia, abdominal pain, nausea, vomiting, diarrhoea, gastritis, gastroenteritis, paraesthesia, stinging sensations in the hands and feet, arterial hypertension, increased blood fat levels, acne, rashes, allergic skin reactions, hyperglycaemia, anaemia, hyperuricaemia, gout, increasing body weight, oedemas, stomach ulcers, convulsions, menstrual disorders, hyperkalaemia, hypomagnesaemia, hot flushes, erythema, itching, muscular cramps, muscular pain, myopathy, etc.
Therefore, it would be desirable, if, for example, after a lung transplantation or in cases of certain other indications, ciclosporin A could be administered in a targeted and tissue specific fashion and so as to achieve only a low systemic bioavailability of the active agent in order to minimize the impact of the active agent on healthy tissue.
A suitable dosage form could also be used for the treatment and prevention of diseases such as asthma, idiopathic pulmonary fibrosis, sarcoidosis, alveolitis and parenchymal lung diseases (see: Drugs for the treatment of respiratory diseases, edited by Domenico Spina, Clive p. Page et. al., Cambridge University Press, 2003, ISBN 0521773210). New therapeutic aspects also result for the topical treatment of possible autoimmune included diseases such as neurodermatitis, psoriasis, unspecific eczema, skin proliferations or mutations, and for the treatment after skin transplantations. An interesting area of application is in the field of ophthalmology, for example, for the treatment after corneal transplants, of ceratoconjunctivitis or other infectious eye diseases which respond partly insufficiently to anti inflammatory therapy, for example with steroids. It is also useful for the treatment of ceratides in animals, such as dogs.
Indeed, attempts have been made to administer ciclosporin locally, for example, in the form of oily eye drops at 1% and 2% (formulation according to the German codex of medicines using refined peanut oil as solubilizer) or as an aerosol. However, this approach normally fails, mainly due to the very low aqueous solubility of the active agent which renders efficient administration considerably difficult. Thus, in the case of pulmonary application, certain adjuvants for solubilization which may be used in the case of oral administration cannot be employed for lack of tolerability. For example, Sandimmun Optoral capsules (Novartis) which contain ciclosporin A, comprise a microemulsion concentrate with ethanol, propylene glycol and significant amounts of surfactants and, therefore, constitute a formulation which, if inhaled, would cause serious toxic effects.
Similarly, the Sandimmun® infusion solution concentrate (Novartis), which is available for infusion, is also not inhalable: The only adjuvants contained therein are ethanol and poly(oxy ethylene)-40-castor oil. It can be used for infusion only because it is previously diluted with a 0.9% sodium chloride solution or a 5% glucose solution, at a ratio of 1:20 to 1:100. This results in large volumes which can be administered by infusion, but not by inhalation.
WO 00/45834 suggests the inhalation of aerosolized ciclosporin for the prevention or treatment of rejection reactions after lung transplants. It is recommended to administer a dose of 15 to 30 mg of ciclosporin A to the lungs. The carrier to be used for the active agent is propylene glycol which, at such a high concentration, results in considerable irritation, which is why the patients are to inhale a solution of lidocainee for local anaesthesia before administration of the ciclosporin preparation. New research (Akkar et al, poster presentation at NACF 2005) shows that, depending on the concentration, propylene glycol kills calu-3 cells which constitute an established model for lung epithelial cells (Steimer et al. Jour. Aerosol Med. 18 (2) pp. 137-182, 2205). Therefore, for physiological reasons, a predominantly aqueous preparation would be desirable.
EP 0 294 239 A1 describes an aqueous preparation of ciclosporin for pulmonary application. In order to increase the solubility, the preparation contains an α-cyclodextrin. However, the solubilisation effect is far to weak for efficient inhalation therapy: the ciclosporin concentrations achieved are only between 0.1 and 2.0 mg/ml, in particular, between 0.2 and 1.5 mg/ml. This means that, administration of a single dose of 20 mg to the lungs might take hours when using a conventional nebuliser.
EP 0 504 760 A1 describes a special orthorhombic crystalline form of ciclosporin A which is said to particularly suitable for inhalation. However, this would be relevant only for inhalation in powder form or for preparations with a dispersion of the active agent, but not for aqueous solutions for nebulisation. Powder inhalers, however, require a comparatively large breathing volume and are poorly suited for the efficient treatment of patients with pulmonary diseases. Moreover, it is known that amounts of powder >20 mg frequently result in coughing and that the respirable fraction of most powder mixtures decreases with increasing concentration of the carrier, such as lactose or trehalose. Furthermore, in view of all known in vitro data, it seems questionable whether the very poorly soluble active agent, if administered to the lungs in the form of suspended particles, will dissolve in the amount of mucus present in the lungs to a sufficient degree which would be a precondition for therapeutic efficacy. The same is true, in principle, for WO 99/42124 which describes an amorphous liquid crystalline ciclosporin.
WO 95/24892 describes a ciclosporin preparation with propellant gas which is to be applied in the form of a dosing aerosol. However, dosing aerosols have been criticized for years since they contributed to global warming and it seems uncertain whether authorizations to market aerosols containing propellant gases will still be given in the mid term. Similar considerations apply to WO 98/01147. It is also known that the respirable fraction decreases when active agents are applied at concentrations of >1 mg/puff and that the dosing accuracy is subject to large variation in vivo. At a pulmonary deposition of only 10% in the case of dosing aerosols, it can be concluded that more than 50 puffs would be required in order to deposit therapeutically relevant ciclosporin concentrations in the peripheral regions of the lungs.
WO 98/00111 proposes a liposomal dispersion of ciclosporin A for inhalation having a very high concentration of phospholipid of up to 225 mg/ml. However, this has such a high dynamic viscosity that it cannot be nebulised efficiently. A liposomal preparation of ciclosporin A is also known from US 2003/0215494: The invention described therein, however, lies in the fact that such a preparation is to be used for the inhibition of pulmonary metastases. This document does not provide a contribution to solving the technical problem of providing a preparation of the active agent which is more suitable for inhalation. U.S. Pat. No. 5,958,378 describes liposomal ciclosporin preparations for nebulisation; however, the viscosity thereof is so high that these cannot be nebulised with an electronic vibrating membrane nebuliser. Moreover, the organic solvent butanol is used for the preparation thereof, but despite a subsequent lyophilisation process, this cannot be removed completely and yields liposomes of >1 μm, which cannot be sterilized by filtration and which have only a low ability to permeate epithelial cell membranes.
Conventional non-liposomal topical preparations, for example, creams, ointments or lotions, do not show sufficient topical efficacy in the treatment of skin diseases such as neurodermatitis or psoriasis because the effect of penetration is insufficient due to scaling and hornification of the epidermis. It is also known that in some cases of these diseases, even liposomal preparations do not necessarily show improved skin permeation, but, depending on the specific composition and the size and nature of the liposomes, yield only insignificant improvements.